TFTs utilizing silicon semiconductor or compound semiconductor are used in general integrated circuits and other expanding applications. In particular, the use of TFTs in liquid crystal displays is well known. The recent trend taken for liquid crystal displays is to increase the display size and the image definition. It has become more desirable than ever to incorporate a multiplicity of TFTs corresponding to the number of pixels.
However, conventional metal-base semiconductors which are used in the art when circuits are formed on substrates cannot avoid introduction of small defects in TFTs formed on the substrate due to photoresist processing steps including patterning and etching. These processing steps impose a certain limit to the desire to reduce the TFT manufacturing cost. The same is true to other flat displays like plasma displays and organic EL displays if TFTs are used therein.
The recent trend toward larger display area and finer image definition leads to a propensity to increase the probability of defects in TFT manufacture. It is strongly desired to minimize TFT defects.
For TFTs having a metal/insulator/semiconductor (MIS) structure, attempts were made to form the insulator and semiconductor from organic substances. For example, JP-A 5-508745 (WO 92/01313) describes that a device fabricated using an insulating organic polymer having a dielectric constant of at least 5 as the insulating layer, and a multi-conjugated organic compound having a weight average molecular weight of up to 2,000 as the semiconductor layer exhibits a field effect and has a mobility of approximately 10−2 cm2V−1s−1.